A common issue when dealing with high bend areas, like the elbow/knee/shoulder/hip, is that no matter how it's constructed or weighted, a corrective blend shape or additional helper joints will eventually be needed to create a more pleasing result.

Using the knee as prime example, you can see the difference in these two legs (Fig.04).

Fig.04 - Density in high blend areas

The leg built for even spans does not have much density to work with to sculpt out a corrective shape for a bent knee (harder edge, 90 degree point and defined knee cap). Whereas the more anatomical leg was created with deformation in mind, leaving enough spans in the mesh to allow a corrective shape.

Finger and Knuckles

Depending on the medium, finger layout can change drastically. From trying to save edge loops for games (Fig.05).

Joshua R. Dodson on Sun, 26 October 2014 8:20pm Thank you this has helped to improve my understanding of Weight painting. In my own personal work I have found that the combination of Basic skin cluster, maya muscle and corrective blend shapes yield highly satisfactory results. It's always a great idea to have a low poly version of your model for animation and simulation testing aside from the full resolution detail model.